Connection of mobile devices to heterogenous networks

ABSTRACT

An improved apparatus for connecting a mobile end system to a communications network includes a mobile end system with storage that is assigned a first unique identity code. An interface with a first transmitter is assigned a second unique identity code and is linked to the mobile end system via a first communications channel. A data switch with a second transmitter is assigned a third unique identity code, and is linked to the interface via a second communications channel. The data switch is also linked to the communications network via a third communications channel. The mobile end system transmits at least the first unique identity code to the interface, which transmits a least the first and second unique identity codes to the data switch, which in turn transmits at least the first, second and third unique identity codes to the communications network. A method of communicating data packets bidirectionally between two mobile end systems or between a mobile end system and a fixed end system through a communications network includes the steps of assigning unique identity codes to each mobile end system and to an interface device and a data witch for each mobile end system, setting up communication channels between the end systems, identifying the routing scheme to be used for the packet transmission, and establishing bidirectional communications between the end systems.

FIELD OF THE INVENTION

This invention relates generally to telecommunication networks, and moreparticularly to the communication of packet data and the connection ofswitched telephone circuits to and from mobile end systems. The mobileend systems may connect to switched circuit networks and packet datanetworks using various interface devices, including telephone circuits,cellular switched radio channels, cellular packet data radio channels,and local area network interfaces.

BACKGROUND OF THE INVENTION

Many telecommunication systems are available for connecting terminalequipment to switched circuit and packet data networks. Most providecommunication services to terminals, or end systems that reside in afixed location, connecting to a network at a topologically restrictedpoint in order to facilitate static routing of packets or calls, forinstance fixed telephone or local area networks. Mobility features havebeen designed into cellular equipment, to support connection of a mobileterminal or end system to a cellular basestation depending on thegeographic area covered by the basestation and the radio path betweenthe basestations and the mobile end system. Cellular systems have beendesigned to provide switched circuit communications, for cellulartelephones as defined in TIA RS-553 specifications, and more recently incellular packet data communications, as defined in the CDPDspecifications.

Interworking requirements for fixed and cellular telephone equipmenthave been developed to provide uniform service, including a uniformnumbering plan and compatible call setup procedures. The North Americancellular industry has developed the RS-553, IS-54, and IS-41specifications for switching systems to allow cellular telephones toroam between cellular switch systems, providing authentication, locationtracking, call routing and setup, and handoff between cellular switchsystems. Similar specifications have been developed for other cellularsystems including European GSM.

Similarly, interworking requirements for fixed and cellular packet datasystems have been developed to provide uniform service, with a uniformaddressing plan and compatible packet transport procedures. Packet datanetworks may include equipment to facilitate the operation ofinterconnected subnetworks using different communications technologies.The Internet protocol stack for TCP/IP communications definescommunications methods that permits different technologies such asEthernet, X.25, satellite, and dialup circuits to interoperate. Packetdata networks can include switched circuit data links using modems andasynchronous communications equipment with X.25 protocol capabilities,or asynchronous communication using the Internet SLIP or PPP protocols.The cellular industry has developed the CDPD specifications for cellulardigital packet data communications to allow mobile end systems to roambetween cellular packet data systems while providing effective packetdata communication services.

A cellular telephone system provides circuit-switched radiocommunication between a stationary cellular switch system and one ormore cellular telephones, and other equipment accessible through theswitched telephone network. Circuit-switched radio communication istypically used to provide voice, facsimile, and data communicationservices. The cellular switch system typically includes equipment forinterconnecting to the switched telephone network, a network ofgeographically separated circuit basestations, circuit-switchingequipment for connecting the telephone network to the basestations,circuit control equipment, and other equipment over radio links, where acall is established between a mobile end system and a basestation. Sucha cellular telephone system is described in the Bell System TechnicalJournal, January 1979, entitled, "The Cellular Concept," page 15, etseq.

Cellular switch systems provide mobile telephone service to cellulartelephones in the geographic areas covered by the basestations. Cellularswitch systems are interconnected by trunking facilities that providecircuit-switched communication paths between base systems, eitherdirectly or through the switched telephone network.

Cellular telephones are mobile, and may roam between geographic areascovered by circuit basestations that are part of different cellularswitch systems. Intersystem signalling procedures following the IS-41standards between cellular switch systems is supported by datacommunication networks that communicate information about the identity,location, and capabilities of roaming cellular telephones between thecontrol equipment at different cellular switch systems. This informationis used to provide circuit-switched communication between cellulartelephones or cellular mobile end systems, without constraining suchservice to the geographic area covered by a single cellular switchsystem.

A cellular packet data system provides packet data radio communicationbetween a stationary cellular packet data system and one or morecellular packet mobile end systems. Packet data radio communicationprovides data communication between fixed end systems and mobile endsystems, or between mobile end systems and other mobile end systems. Acellular packet data system typically includes equipment forinterconnecting to one or more packet data networks, a network ofgeographically separated packet basestations, packet switchingequipment, and other equipment. A cellular packet data system uses oneor more radio channels that are shared by several mobile end systems,for transmission of data in bursts between the mobile end systems and abasestation. Interconnection to fixed packet data networks may beprovided over various suitable communication media.

Cellular packet mobile end systems are typically portable, and may roambetween geographic areas covered by packet basestations that are part ofdifferent cellular packet data systems. Data communication betweencellular packet data systems communicates information about theidentity, location, and capabilities of roaming packet mobile endsystems between data switches at different cellular packet data systems.This information is used to provide data communication to cellularpacket mobile end systems, without constraining such service to thegeographic area covered by a single cellular packet data system.

A cellular packet data system may operate independent of any cellularswitch system, or may interconnect with the cellular telephone system toshare common equipment or resources, e.g., radio channel assignment,antennae or telephone interface equipment. One method of interconnectinga cellular telephone system and a cellular packet data system isdescribed in U.S. patent application Ser. No. 07/674,660, filed Mar. 25,1991, now abandoned.

One weakness of the current cellular switch system and cellular packetdata system technology is the inability to provide packet data coverageto mobile end systems outside of the area of coverage of the cellularpacket data system. It is desired to use switched circuit cellularequipment to provide an alternate means of access to packet datanetworks, in areas not covered by cellular packet data systems, or touse fixed telephone circuits or local area network interfaces whereneither cellular nor cellular packet coverage is available. Currentswitching equipment cannot offer solutions to these requirements.

A cellular remote unit may operate independent of any packet remoteunit, or the two remotes may be integrated to share common equipment orresources. Typically, circuit-switched and packet mobile end systems areintegrated, such that parts of the radio equipment are shared betweencircuit-switched and packet usage. A mobile end system will use a singleradio channel to provide either switched circuit or packetcommunication, but cannot provide both simultaneously. When the radiochannel is used for circuit-switched communication, packet communicationservices cannot be provided, and when the radio channel is used forpacket communication, circuit-switched communication services cannot beprovided. It is desired for a mobile end system to be able to receiveswitched circuit calls while monitoring a cellular packet data radiochannel, and to transparently switch to switched circuit operation whenan incoming call arrives, or when the use of switched circuit cellularequipment would provide superior performance or lower cost for thecommunications service. Current equipment cannot offer this service.

A variety of methods exist in prior art for providing reliable switchedcircuit data communication over cellular channels, as described inseveral U.S. Patents. These methods offer routing only within thecontext of the switched circuit network, including fixed and cellularsubnetworks, and do not support interconnection of switched cellulardata communication devices to packet data networks, or routing of packetdata to mobile switched cellular data communications equipment.Reference is made in this regard to U.S. Pat. Nos. 5,159,592 granted toIBM and 4,837,800 granted to Motorola, Inc.

SUMMARY OF THE INVENTION

The invention resides in interconnecting a mobile end system to acommunication network that includes a packet data network and mayinclude a telephone network, using various interface devices tocommunicate packet data between the mobile end system and the packetdata network, and to connect switched circuits between the mobile endsystem and the telephone network. Suitable interface devices may includea cellular telephone, a packet data cellular module, a telephoneinterface, and a local area network interface, among others.

Each mobile end system will be identified by an address within thepacket data network, and optionally by an address within the telephonenetwork. Packet switches will receive data packets from variouscommunication links, and route these data packets to mobile end systems,to fixed end systems, to external network gateways, or mobile networksupport elements including mobile location registers and routers. Datapackets will include the address of the mobile end system or fixed endsystem to which the data packet is to be delivered.

The mobile end system connects to an interface device to determine thelocation of the mobile end system. The mobile end system and interfacedevice will communicate the location information to a mobile locationregister.

The mobile location register will store the most recent locationinformation for mobile end systems, identifying the routing required foraccess to the connected interface device, and may additionally qualifythe location of the mobile end system with respect to the point ofinterconnection. For example, location information for a mobile endsystem that is connected to a telephone interface would include thedirectory number of this interface.

The mobile location register will communicate current locationinformation to tables maintained by routers, enabling the routing ofdata packets to an interface device, which then delivers the packets tothe mobile end system.

Using this mobile packet communication system, additional features thatsupport routing of switched-circuit calls to mobile end systems can beprovided, and methods for connecting the switched circuit path aredescribed. Specific methods for interworking of cellular switchedcircuit and cellular packet data networks are also described.

Several objects and advantages of preferred aspects of the inventioninclude the following:

(a) provision of switched circuit service and packet data communicationin a network composed of interconnected subnetworks, where the mobileend system can move between or select between various subnetworks,

(b) communication of packet data between mobile end systems and fixedend systems, where the mobile end systems move between geographic areascovered by different subnetworks, which may include cellular packetdata, cellular telephone, telephone circuits, and local area networks,

(c) communication of packet data between mobile end systems and fixedend systems, where the mobile end system selects or may be cause to beselected one or more of the available subnetworks,

(d) communication of packet data between mobile end systems and othermobile end systems, where the mobile end systems may move between orselect the communication access means as described in (b) and (c),

(e) establishment of switched circuit connections to mobile end systems,where the mobile end system in question may be communicate signallinginformation through cellular packet data, fixed telephone circuits, andlocal area networks,

(f) routing of voice or other switched circuit telephone calls,dependent on the current location of a mobile end system, and

(g) switching from a shared packet data radio to a switched circuitchannel for higher performance or lower cost.

According to the present invention then, there is provided an apparatusfor connecting a mobile end system to a communications networkcomprising a mobile end system incorporating storage means and havingassigned thereto a first unique identity code, an interface deviceincluding a first transmission means and having assigned thereto asecond unique identity code, said interface device being linked to saidmobile end system via a first communications channel, and data switchmeans including a second transmission means and having assigned theretoa third unique identity code, said data switch means being linked tosaid interface device via a second communications channel and beingadditionally linked to said communications network via a thirdcommunications channel, wherein said mobile end system communicates withsaid interface device by transmitting at least said first uniqueidentity code thereto and wherein said interface device communicateswith said data switch by transmitting at least said first and secondunique identity codes thereto and communicating said third uniqueidentity code as well as said first and second unique identity codes tosaid communications network.

According to another aspect of the present invention, there is alsoprovided a method of communicating data packets bidirectionally betweena mobile end system and either a fixed end system or another similarmobile end system, said mobile end system being coupled to one or moresubnetwork communication devices to communicate with a circuit switchednetwork or packet data network, said method comprising the steps ofassigning unique identity codes to at least said mobile end system, toan interface device and to a data switch means, setting up communicationchannels between an originating device and a terminating device,identifying the routing to be used for packet transmission, establishingbidirectional communications between an originating device and aterminating device.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing the configuration of the mobile endsystem and other components of the present invention.

FIG. 2 is a block diagram showing the connections of the components ofthe mobile routing network of the present invention.

FIG. 3 is a flowchart showing the procedure executed by the mobile endstation to transmit or cause to be transmitted its current location.

FIG. 4 is a block diagram of the mobile data circuit switch.

FIG. 5 is a flowchart of the procedure executed by the mobile routingregister on receiving location information for a mobile end system

FIG. 6 is a block diagram of the system components required forconnection of switched circuits and packet networks.

FIG. 7 is a flowchart of the procedure required for establishment of aswitched circuit call to a mobile end system.

FIG. 8 is a block diagram for a mobile end system.

FIG. 9 is a flowchart of the procedure executed by the mobile end systemfor handling incoming switched circuit calls.

DETAILED DESCRIPTION OF THE INVENTION

System Overview

Referring first to FIG. 1, the network system of the present inventioncomprises four primary devices: a mobile end system 102, a telephoneaccess gateway 104, a local area network access gateway 107, and amobile routing network 101. Components of the system that derivesubstantially from prior art are a fixed telephone 124, a circuitswitched network 103, a packet data network 108, a cellular packet datasystem 106, a cellular switch system 105, and a fixed end system 125.The network system is designed to route data packets bidirectionallybetween mobile end system 102 and fixed end system 125, and also betweenmobile end system 102 and other similar mobile end systems of similardesign. The network system is also designed to connect switched circuitsbetween mobile end system 102 and fixed telephone 124, and also betweenmobile end system 102 and other mobile systems of similar design.

Mobile end system 102 connects to one or more subnetwork communicationdevices, which as shown in FIG. 1 may include telephone access gateway104, cellular switch system 105, cellular packet data system 106, andlocal area network access gateway 107, which provide communicationcapabilities to mobile end system 102, allowing it to communicate withcircuit switched network 103 and packet data network 108.

Circuit switched network 103 may be a conventional public or privatenetwork of telephone switching equipment and interconnecting facilitiesthat provides the means for setting up a switched circuit connectionbetween an originating device and a terminating device, and forproviding bidirectional communication between these two devices. Circuitswitched network 103 connects switched circuits between its connectedterminal devices, including fixed telephones, according to addressing ordialing information provided by the originating terminal. A numberingplan is established that allows circuit switches within circuit switchednetwork 103 to route calls from the point of origination to the point oftermination, according to the dialled number and the network topology.

Likewise, packet data network 108 may be a conventional public orprivate network of packet data switching equipment and interconnectingfacilities that provides the means for sending packets of data from asource device to a destination device. The mobile networking systemdescribed here assumes that the packet data network 108 follows theTCP/IP specifications. Packet data network 108 routes data packetsaccording to the destination address contained in each packet, andstatic or slowly changing routing tables that associate a destinationaddress with a physical subnetwork. The addressing plan for a TCP/IPnetwork is hierarchical, and inherently links destination addresses tothe network topology.

A mobile routing network 101 routes packet data from packet data network108 to mobile end system 102, and supports call establishment to mobileend system 102. Mobility is supported by allowing packet data andswitched circuit calls to be routed according to the current location ofmobile end system 102, rather than routing according to networktopology.

One or more telephone circuits 122 connect a fixed telephone 124 tocircuit switched network 103. One or more telephone circuits 111 connectcircuit switched network 103 to cellular switch system 105. One or moretelephone circuits 109 connect circuit switched network 103 to mobilerouting network 101.

The source and destination points of packet data network 108 may be,variously, fixed end system 125, cellular packet data switch 106, localarea network access gateway 107, and mobile routing network 101. One ormore packet data links 115 connect mobile routing network 101 to packetdata network 108. One or more packet data links 123 connect fixed endsystem 125 to packet data network 108. One or more packet data links 113connect packet data network 108 to local area network access gateway107. One or more packet data links 112 connect packet data network 108to cellular packet data system 106.

A telephone access link 118 connects mobile end system 102 to telephoneaccess gateways 104. Telephone access link 118 is a point to point link,and may incorporate an electrical cable, a radio link, or optical linkand associated interface devices to provide bidirectional communicationbetween telephone access gateway 104 and mobile end system 102 forsignalling information required for call setup and release, and bearerservices including transmission of voice, data, facsimile, and otherservices compatible with the telephone network.

A local area network access link 121 connects mobile end system 102 tolocal area network access gateway 107. Local area network access link121 is a point to point link, and may incorporate an electrical cable, aradio link or optical link and associated interface devices as a meansfor providing bidirectional communication between local area networkaccess gateway 107 and mobile end system 102.

Mobile end system 102 may be connected from time to time to one or moretelephone access gateway 104, cellular switch system 105, cellularpacket data system 106, and local area network access gateway 107. Oneor more cellular circuit radio channels 119 connect mobile end system102 to cellular switch system 105. Cellular circuit radio channel 119 isused by cellular switch system 105 and mobile end system 102 forestablishment of calls between cellular switch system 105 and mobile endsystem 102, including registration for transmitting the current locationof mobile end system 102 to cellular switch system 105, andcommunication of signalling information including establishment,handoff, and disconnection of calls between cellular switch system 105and mobile end system 102, and bearer services including voice, data,facsimile, and other services compatible with the telephone network.

One or more cellular packet radio channels 120 connect mobile end system102 to cellular packet data system 106. Cellular packet radio channel120 provides registration means for transmitting the current location ofmobile end system 102 to cellular packet data system 106, and fortransmitting packet data between cellular packet data system 106 andmobile end system 102. Use of radio channel 120 is typically shared byone or more mobile end systems 102.

Mobile end system 102 may select one or more of the available means ofcommunication, depending on its configuration, availability of thedesired network service, the cost of communication services, and userrequests. FIG. 8 shows a block diagram of mobile end system 102. Acellular radio 811 provides a single interface for both cellular circuitradio channel 119 and cellular packet radio channel 120. Signalprocessing and lower layer protocols required for the cellularinterfaces are provided by a cellular circuit channel processor 808 anda cellular packet data channel processor 809. Interfaces to telephoneaccess link 118 and local area network access link 121 are provided by atelephone access interface 801 and a local area network access interface810, respectively. Switched circuit paths from telephone accessinterface 801 and cellular circuit channel processor 808 are switched byan audio path switch 802, which connects either cellular circuit channelprocessor 808 or cellular packet data channel processor 809 to either anaudio processor 803 and its attached speaker and microphone, shown as ahandset 804, or to a modem and packet processor 807. Packet flow to andfrom packet processor 807, telephone access interface 801, and localarea network access link 121 is routed to a packet protocol control 805,which performs higher layer protocol processing, for example accordingto TCP/IP specifications. A host computer 812 is connected to packetprotocol control 805 to control, send, and receive data. A mobile endsystem control 813 controls the operation of all components of mobileend system 102.

Typically, use of cellular circuit radio channel 119 and cellular packetradio channel 120 will be mutually exclusive as a consequence of sharedinternal radio equipment between these two communication functions andincompatibilities between simultaneous use of both. Mobile end system102 may select one of these, or it may alternate between monitoringcellular circuit radio channel 119 and cellular packet radio channel120. If mobile end system 102 alternates between monitoring cellularcircuit radio channel 119 and cellular packet radio channel 120, thetiming of this function may be synchronized with sleep procedures, asdefined in the CDPD specification for cellular packet radio channels,that may be executed by cellular packet radio channel 120.

Mobile routing network 101 is responsible to determine and store thecurrent location of mobile end system 102, for routing for data packetsto mobile end system 102, and for routing switched circuit calls tomobile end system 102.

Mobile Routing Network

Referring to FIG. 2, mobile routing network 101 stores the currentlocation of mobile end system 102 in a mobile routing register 203. Thecurrent location includes information required to identify the means ofconnection for packet data communication to the mobile end system 102,and additional information that further identifies the location of themobile end system 102 relative to the means of connection. The specificinformation is dependent on the nature of the subnetwork to which mobileend system 102 connects, but will typically include mobile end systemidentification, subnetwork identification, subnetwork addressing such asa telephone number, additional location information such as cellularsystem identification or cell site identification, and bearer servicecapabilities presented by the subnetwork connection device, for examplevoice communication service. Mobile end system 102 communicates with thesubnetwork connection device to determine its current location andinitiate procedures for transmitting its current location through thenetwork system to mobile routing register 203.

Mobile routing register 203 receives and stores current locationinformation from a home location register 206 via a data link 213, acellular packet data mobile serving function 204 via a data link 205,packet data network 108 via a packet data link 115, and a mobile datacircuit switch 208 via a data link 214. By distributing routinginformation to selected system components, which may be geographicallydispersed through mobile routing network 101, mobile routing register203 facilitates subsequent routing of packet data. Mobile routingregister 203 sends routing information to a source mobile packet router209, a destination mobile packet router 210, and mobile data circuitswitch 208 according to the current location information and networkconfiguration information maintained by the mobile routing register.

Cellular packet data mobile serving function 204 executes the proceduresrequired by its interface to cellular packet data system 106 forredirecting packet data from within the cellular packet data system 106to mobile routing network 101 over a data link 205. Two procedures,defined in the CDPD specification, may be used to redirect thesepackets. The first procedure provides for exchange of locationinformation between mobile routing register 203 and cellular packet datasystem 106. The second procedure provides for the forwarding of packetsreceived by cellular packet data mobile serving function 204 fromcellular packet data system 106 to source mobile packet router 209 overa data link 216. Packets that are forwarded in this manner areencapsulated within a forwarding IP packet header, to permit theirrouting by packet data network 108 according to the forwardingdestination address.

Home location register 206 executes the procedures required by cellularswitch system 105 to route circuit switched calls to mobile data circuitswitch 208 for connection to mobile end system 102. These proceduresconform to the IS-41 specifications for intersystem call delivery.

Packet data is routed by the mobile routing network 101 from sourcemobile packet router 209 to destination mobile packet router 210. If thepacket is to delivered to mobile end system 102 via cellular switchsystem 105 or telephone access gateway 104, the packet will be routedfrom destination mobile packet router 210 to mobile data circuit switch208. If sufficient routing information is not available at source mobilepacket router 209 to forward directly to destination mobile packetrouter 210, other routing steps will be required, as will be shown.

Packet data is received by source mobile packet router 209 from packetdata network 108 over packet data link 115 and routed according torouting information stored by source mobile packet router 209. Packetdata is routed from source mobile packet router 209 to destinationmobile packet router 210 by forwarding the packet data through packetdata network 108. If no routing information for mobile end system 102 isavailable, source mobile packet router 209 will forward the packet to asecond destination mobile packet router 210, where by default currentrouting information will be maintained. If mobile end system 102 isaccessible from the recipient destination mobile packet router 210,destination mobile packet router 210 delivers the packet data totelephone access gateway 104, cellular switch system 105, cellularpacket data system 106, or local area network access gateway 107,according to the routing information stored by destination mobile packetrouter 210. Otherwise, if the destination mobile packet router 210 isthe default and mobile end system 102 is not directly accessible fromthis router, the routing table will identify a third destination mobilepacket router 210 that can deliver to mobile end system 102, and thepacket will be forwarded to this third destination mobile packet router210.

Mobile data circuit switch 208 routes packet data between a data link218 that connects mobile data circuit switch 208 to destination mobilepacket router 210, and mobile end system 102 over a telephone circuit109 to either telephone access gateway 104 or cellular switch system105.

Mobile Data Circuit Switch

FIG. 4 shows the components of a mobile data circuit switch in greaterdetail.

A mobile circuit routing table 401 stores information about each mobileend system 102 that is accessible from mobile data circuit switch 208via one or more telephone circuits 109 and circuit switched network 103.The information stored in mobile circuit routing table 401 may includethe directory number or cellular mobile identification number forcircuit switched network 103 to reach telephone access gateway 104 orcellular switch system 105 that mobile end system 102 has selected asthe preferred subnetwork connection device.

A circuit switch 407 connects telephone circuit 109 to a modem 406 overa circuit 415, and connects pairs of telephone circuits 109 to eachother.

Modem 406 converts data received over a data link 413 from a packetencoder 408 to an analog signal that is transmitted to circuit switch407, and converts analog signals received from circuit switch 407 todata that is sent to a packet decoder 405 via a data link 414. Modem 406may additionally include appropriate forward error correction,retransmission, and compression logic if desired. Many suitable modemdevices with these capabilities are available, with link layer protocolssuch as Microcom's MNP 4, MNP 5, and MNP 10 protocols, or the CCITT V.42or V.42bis standards.

Packet encoder 408 formats data taken from a transmit buffer 403 over adata link 411, for transmission to mobile end system 102 via modem 406in accordance with the network layer packet protocol in use, for examplethe Internet SLIP or PPP protocols. Packet decoder 405 removesformatting from the data received from mobile end system 102, inaccordance with the packet protocol in use.

Transmit buffer 403 stores packet data received from destination mobilepacket router 210 over data link 218 until it can be transmitted tomobile end system 102, or for a maximum time. The maximum time isdetermined by analysis of the data content of the data in the transmitbuffer. As outlined here the packet data will conform to the Internet IPprotocol, and a maximum time to live is contained in these packetheaders.

Receive buffer 404 stores packet data received from mobile end system102 via packet decoder 405 and data link 412, until it can betransmitted to packet data network 108 over a packet data link 115. Amaximum time to live timer may be implemented in receive buffer 404.

A mobile circuit control 402 executes procedures required forcommunication with mobile end system 102, such as initiating connectionof switched circuits to mobile end system 102 via telephone circuit 109,answer incoming calls over telephone circuit 109, and connect modem 406to telephone circuit 109, by exchanging messages with circuit switch 407over a control and signalling link 410. Mobile circuit control 402updates mobile circuit routing table 401 with information about thecurrent switched connections to mobile end systems 102 over telephonecircuits 109. Mobile circuit control 402 also updates the mobile circuitrouting table 401 according to requests received from the mobile routingregister 203 over data link 215.

Mobile circuit routing table 401 stores information about the routing ofdata from circuit switch 407 and mobile end system 102. This informationwill indicate the identity of connected telephone circuit 109 if aswitched circuit is currently established to mobile end system 102, andwill also include the directory address in circuit switched network 103that should be used to establish a switched circuit to mobile end system102. Temporary directory numbers may be assigned by mobile circuitcontrol 402 and stored in mobile circuit routing table 401.

Transmitting Current Location to the Mobile Routing Register

Referring to FIG. 3, mobile end system 102, in block 301 determines itscurrent location and available connection means by monitoring the stateof one or more configured subnetwork connection devices: telephoneaccess link 118, cellular circuit radio channel 119, cellular packetradio channel 120, and local area network access link 121. In general,these subnetwork connection devices may incorporate stored addressing orlocation information, if they provide a permanent point of connection totheir respective networks, or may determine a temporary address bycommunication with the network. In block 302, mobile end system 102checks that at least one of these subnetwork connection devices canprovide packet data service. If one or more can provide this service,mobile end system 102 selects the preferred subnetwork connection devicein block 303, typically making this decision based on information aboutthe communications needs, cost, and user preferences.

If cellular switching system 105 is selected as the preferred subnetworkconnection device, then in block 307 mobile end system 102 initiates theregistration procedure required by cellular switch system 105 tocommunicate the current location of mobile end system 102 over cellularcircuit radio channel 119 to cellular switch system 105. The currentlocation is stored by cellular switch system 105. When it complete itspart of the registration procedure, cellular switch system 105 transmitsthe current location of mobile end system 102 to home location register206, over cellular intersystem signalling link 116. Home locationregister 206 then transmits the current location of mobile end system102 to mobile routing register 203 over data link 213. Communicationsover the cellular intersystem signalling link 116 follow the proceduresrequired for interconnection to the cellular switch system 105, andtypically use a standard network protocol such as X.25 or signallingsystem 7. Home location register 206 stores the current location ofmobile end system 102 in its memory and may communicate with othercellular switch systems for the purpose of conveying cellular callrouting information to these systems. The procedures followed bycellular switch system 105 and home location register 206 are defined byTIA IS-41 specifications.

If cellular packet data system 106 is selected as the preferredsubnetwork connection device, then in block 308 mobile end system 102initiates the registration procedure required by cellular packet datasystem 106 to communicate the current location of mobile end system 102over cellular packet radio channel 120 to cellular packet data system106. The current location is stored by cellular packet data system 106.Once it has completed its end of the registration procedure, cellularpacket data system 106 transmits the current location of mobile endsystem 102 to cellular packet data mobile serving function 204, overcellular packet data system link 117. Cellular packet data mobilelocation register 204 then transmits the current location of mobile endsystem 102 to mobile routing register 203 over data link 205. Theseprocedures conform to the requirements of the CDPD specification, for amobile serving function.

If telephone access gateway 104 is selected by mobile end system 102 asthe preferred subnetwork connection device, then in block 309 mobile endsystem 102 initiates a switched circuit call to mobile data circuitswitch 208, through telephone access gateway 104, telephone circuits 109and 110 and circuit switched network 103. In block 310 mobile end system102 transmits its current location to mobile data circuit switch 208over telephone circuit 109. Mobile end system 102 may disconnect thecall after the transmitting the current location as shown in block 311,or optionally may remain connected if further communication isanticipated. Mobile data circuit switch 208 then transmits the currentlocation of mobile end system 102 to mobile routing register 203 overdata link 214. If mobile end system 102 remains connected, mobile datacircuit switch 208 will update its mobile circuit routing table 401accordingly.

If local area network access gateway 107 is selected by mobile endsystem 102 as the preferred subnetwork connection device, then in block312 mobile end system 102 transmits its current location to mobilerouting register 203, through local area network access gateway 107,packet data links 113 and 115 and packet data network 108.

Transmission of Routing Information

Mobile routing register 203, on receiving the current location of mobileend system 102 executes the procedure shown in FIG. 5. In block 501mobile routing register 203 selects a first destination mobile packetrouters 210 to route packet data to mobile end system 102 according toits current location.

Mobile routing register 203 will then, in block 502 send a route flushrequest to a second destination mobile packet router 210, causing thissecond destination mobile packet router to remove the entry for mobileend system 102 from its memory.

In block 503 mobile routing register 203 sends a request to firstdestination mobile packet router 210, with the information required toadd an entry for mobile end system 102 to its routing tables. This tableentry will identify mobile data circuit switch 208, cellular packet datasystem 106, or local area network access gateway 107 as the preferredsubnetwork connection device for delivery of packets to mobile endsystem 102. Routing information is sent to mobile circuit routing table401 if required. In block 503 mobile routing register 203 will also senda routing table update to a third destination mobile packet router 210that is designated as the default routing point.

According to the preferred subnetwork connection device indicated bymobile end system 102 in its current location information, mobilerouting register 203 may in block 504 decide to send location updateinformation to cellular packet data system 106 in block 507, viacellular packet data mobile serving function 204, data link 205, andcellular packet data system link 117, or to send location updateinformation to local area network access gateway 107 via packet links113 and 115, and packet data network 108.

Routing of Data Packets and Dynamic Updating of Routing Tables

Packet data is routed from a source mobile packet router 209 to adestination mobile packet router 210 by forwarding the packet datathrough packet data network 108, via packet data link 115. Forwardedpackets are encapsulated in a forwarding packet so that packet datanetwork 108 can deliver the packet to the correct destination mobilepacket router 210. Destination mobile packet router 210 extracts theencapsulated packet, then analyzes the destination address specified inthe packet header to determine the correct routing for the packet data.

If the destination address is a subnetwork connection device that isdirectly accessible from destination mobile packet router 210, thendestination mobile packet router 210 delivers the packet data to mobiledata circuit switch 208, cellular packet data system 106, or local areanetwork access gateway 107, according to the packet data destinationaddress and the routing information stored in destination mobile packetrouter 210. If the destination address is not one of the above, thendestination mobile packet router 210 will forward the packet data to thedefault destination mobile packet router 210, determined from the packetaddress for the mobile end system 102, and send a route flush request tosource mobile packet router 209.

If forwarded packet data is received by a first default destinationmobile packet router 210 from a source mobile packet router 209, and theprevious procedure determines that the packet data is to be forwarded toa second destination mobile packet router 210, then the firstdestination mobile packet router 210 will send a routing table update tosource mobile packet router 209, identifying the destination mobilepacket router 210 that can directly route the packet data. When sourcemobile packet router 209 receives the table update message, it will addor modify its routing table entry for mobile end system 102.

Routing information maintained by source mobile packet router 209 anddestination mobile packet router 210 may be deleted from time to time,according to internal algorithms of these devices, provided that adefault destination mobile packet router 210 always maintains itsrouting tables such that they match the current location maintained bymobile routing register 203.

Packet Delivery over Switched Circuits

When a packet is sent from destination mobile packet router 210 tomobile data circuit switch 208 over data link 218, the packet is sent tomobile end system 102 through circuit switched network 103 and eithertelephone access gateway 104 or cellular switch system 105, depending onthe information in mobile circuit routing table 401. When the packetarrives in transmit buffer 403, mobile circuit control 402 retrieves thetable entry corresponding to the packet destination address from mobilecircuit routing table 401. If there is a circuit currently establishedbetween circuit switch 407 and mobile end system 102, and this circuitis connected to modem 406, then the packet is queued in transmit buffer403 for transmission through packet encode 408 and modem 406, to mobileend system 102. If there is a circuit currently established, and it isconnected to telephone circuit 109 indicating that a voice call or otherswitched circuit call is in progress, the packet will be discarded. Ifthere is no call currently in progress the procedures for connection toeither telephone access gateway 104 or cellular switch system 105.

To establish a call to telephone access gateway 104, mobile circuitcontrol 402 selects a telephone circuit 109 and commands circuit switch407 to initiate a call to mobile end system 102, using the directorynumber given in mobile circuit routing table 401, corresponding to thedestination address in the packet.

To establish a call to cellular switch system 105, mobile circuitcontrol 402 sends a route request message, containing the cellularmobile identification number for mobile end system 102, to cellularswitch system 105. The response to this request provides a temporarylocal directory number, and this number is used to establish the call tomobile end system 102. Mobile circuit control 402 selects a telephonecircuit 109 and commands circuit switch 407 to initiate a call to mobileend system 102, using the temporary directory number. This procedureconforms to the requirements of the IS-41 specification for intersystemcall delivery.

In either case, when the call is established, modem 406 initiates atraining handshake with a modem 807 in mobile end system 102, and whenthis is complete packets in transmit buffer 403 are transmitted.Received packets are verified in a packet decoder 405 and placed in areceive buffer 404 for transmission over packet data link 115 to packetdata network 108. As noted earlier, the time to live field in thepackets stored in transmit buffer 403 and receive buffer 404 will bedecremented periodically, and when they reach zero the packet will beremoved from transmit buffer 403 or receive buffer 404 and discarded.

Packet Delivery to Local Area Network Access

When destination mobile packet router 210 determines that a packet is tobe delivered to local area network access gateway 107, the packet isencapsulated in a packet addressed to local area network access gateway107, which has a fixed location within the address plan used by packetdata network 108. When the encapsulated packet arrives at local areanetwork access gateway 107, the encapsulated packet is extracted and thepacket is delivered to mobile end system 102 over local area access link121.

Packet Delivery to Cellular Packet Data System

Static routing tables are sufficient to route packets to the home mobilefunction in cellular packet data system 106, in accordance with therequirements of the CDPD specification. Internal routing will result inencapsulated packets being forwarded to the appropriate mobile servingfunction, to be sent across cellular packet radio channel 120 to mobileend system 102. Note that, because of the structure of the system withthe mobile routing network 102 incorporating the CDPD mobile servingfunction rather than a CDPD mobile home function, it is in general notrequired for the mobile routing network 101 to route packets fordelivery to the cellular packet data system.

Circuit Switched Calls

FIG. 6 shows those parts of the network system that participate indelivering circuit switched calls to mobile end system 102 from circuitswitched network 103.

The procedures executed by source circuit switch 603 are compatible withthe TIA IS-41 specification for intersystem operations. A call isoriginated from a fixed telephone 124 or other point in circuit switchednetwork 103. The call is routed from circuit switched network 103 tosource circuit switch 603 over a telephone circuit 109, according to thedirectory number provided by the originating point and the numberingplan for the network and associated with mobile end system 102. Sourcecircuit switch 603 then sends a location request message, including thedirectory number for mobile end system 102, to home location register206 over data link 602. Home location register 206 then retrieves thecurrent location of mobile end system 102 from its memory and selects amobile data circuit switch 208 for establishing a switched circuit tomobile end system 102. Home location register 206 may also infer specialbearer service requirements from the given directory number. Specificbearer services may include voice, facsimile, and circuit data.

Home location register 206 then sends a route request message to mobilecircuit control 402 in a mobile data circuit switch 208 over a data link601, including the mobile identification, current location, and anindication of the requested bearer services. Mobile circuit control 402will then reserve the resources required to service the call and assigna temporary local directory number. Mobile circuit control 402 sends thetemporary local directory number to home location register 206 over datalink 601. Home register 206 then forwards the temporary local directorynumber to source circuit switch 603 over data link 602.

Source circuit switch 603, on receiving the temporary local directorynumber, initiates a call using the temporary local directory number toroute the call to circuit switch 407 through a telephone circuit 605, acircuit switched network 103, and a telephone circuit 604. Sourcecircuit switch 603 connects a voice path between telephone circuits 109and 605. Circuit switch 407 reports the arrival of the incoming call tomobile circuit control 402 over signalling link 410.

Mobile circuit control 402 then executes the procedure in FIG. 7 toroute the call to mobile end system 102. Block 701 is executed accordingto the preferred subnetwork connection device. As shown in the flowchartthe procedures for routing calls through cellular switch system 105 ortelephone access gateway 104 to mobile end system 102 are similar. Inthese cases, block 703 is executed to determine if mobile end system 102is currently busy, and if it is busy circuit switch 603 connectstelephone circuit 604 to a busy tone generator 606 in block 704.Otherwise block 705 is executed to determine if the call path can bedirectly connected to the mobile end system 102. If the circuitconnection is determined to support voice only bearer services, block706 is executed to connect the call to mobile end system 102.

The method executed for block 706 differs for calls that are terminatedthrough cellular switch system 105 and calls that are terminated throughcircuit switched network 103 and telephone access gateway 104. In theformer case mobile circuit control 402 sends a route request message tocellular switch system 105 over cellular intersystem signalling link116. Cellular switch system 105 replies by sending a temporary localdirectory number to mobile circuit control 402. Mobile circuit control402 then initiates a call to cellular switch system 105, using thetemporary local directory number to route the call through a telephonecircuit 109, a circuit switched network 103, and a telephone circuit 111to cellular switch system 105. Mobile circuit control 402 commandscircuit switch 407 to connect telephone circuit 109 to telephone circuit604.

If block 706 is executed for a call that is terminated through circuitswitched network 103 and telephone access gateway 104, mobile circuitcontrol 402 initiates a call to telephone access gateway 104, using thedirectory number of telephone access gateway 104, which is identified inthe entry in mobile circuit routing table 401 for mobile end system 102,to route the call through a telephone circuit 109, a circuit switchednetwork 103, and a telephone circuit 110 to telephone access gateway104. Mobile circuit control 407 commands circuit switch 407 to connecttelephone circuit 109 to telephone circuit 604.

If it was determined in block 705 that mobile end system 102 supportsvoice and packet data calls, mobile circuit control 402 proceeds toblock 707, where mobile circuit control 402 commands circuit switch 603to connect telephone circuit 604 to a ringback tone generator 607, andin block 707 a data call is initiated to mobile end system 102. Theprocedures for initiating this data call follow the procedure describedabove for block 706. Circuit switch 407 connects the new call to a modem406. Data packets identifying the desired bearer services aretransmitted over modem 406 to offer the call to mobile end system 102 inblock 708. If the call is answered in block 709, then in block 710mobile circuit control 402 commands circuit switch 407 to connecttelephone circuit 109 to telephone circuit 604, and to provide answersupervision over telephone circuit 604.

Routing of circuit calls when the preferred subnetwork connection deviceis local area network access gateway 107 does not, in general allowestablishment of a circuit the same communication medium as packet datacommunications, although high performance local area network technologywill support this. In general, the current invention allows a nearbytelephone, facsimile equipment, or similar facility to be identified asthe terminating point for switched circuit calls, for a predeterminedbearer service. If it was determined in block 702 that the preferredsubnetwork connection device is local area network access gateway 107,then the call is routed in block 711 to an associated fixed telephone124 that is identified in a system configuration database as associatedwith local area network access gateway 107 for the requested bearerservice. The procedure executed in block 711 initiates a call through atelephone circuit 109, a circuit switched network 103, and a telephonecircuit 122.

If it was determined in block 712 that the preferred subnetworkconnection device is cellular packet data system 106, then in block 714the call is offered to mobile end system 102 by sending data packetsrequesting the desired bearer services over packet data link 115 tocellular packet data system 106, through packet data network 108.Procedures for routing packet data to mobile end system 102 have beendescribed in an earlier section. If the call is answered in block 712,as indicated by signalling data packets received over packet data link115 from mobile end system 102, via cellular packet data system 106, andpacket data network 108, then in block 713 the call is passed tocellular switch system 105 following the intersystem handoff procedures.Suitable handoff procedures are defined in TIA IS-41 specifications.

Mobile End System Call Handling

FIG. 9 shows a flowchart for the procedure followed by mobile end systemcontrol 813 when it receives a voice call from mobile data circuitswitch 208. This procedure entails the transmission of signallingpackets mixed with packet data, using the signalling packets to offerthe voice call to the user. The incoming call is received, and mobileend system control 813 answers in block 901. Following the call setupprocedures from TIA RS-553 for an incoming cellular call, if applicable,the mobile end system control 813 tunes a cellular radio 811 to thevoice channel. In block 902 mobile end system control 813 enables acellular channel processor 808, or telephone access interface 801, andestablishes a path through an audio path switch 802 to a modem andpacket processor 807, and initiates a modem training handshake for modemand packet processor 807. In block 903 a packet is received by modem andpacket processor 807. Mobile end system control 813 inspects the packetin blocks 904 and 906. If it is not a signalling packet it is deliveredto a packet protocol processor 805 for processing according to theInternet IP protocol specification. Call setup packets are interpretedby mobile end system control 813. In block 907 an indication of theincoming call is provided. This indication may be an audio ringing tonegenerated by an audio processor 803 and sounded in a handset 804, astatus indication to a host computer 812, or other indication to higherlevel software or the user that a voice call is being offered. Mobileend system control 813 then waits in block 908 for the call to beanswered by the user or host computer in block 909. It then sends ananswer signalling packet from modem and packet processor 807 to thecellular circuit radio channel 119, to be subsequently communicated tomobile data switch 208, which signals answer supervision on incomingtelephone circuit 604. In block 911 mobile end system control 813disconnects the modem path through audio patch switch 802, connectingcellular circuit channel processor 808 to audio processor 803. Theswitched circuit is then complete, and in the case of a voice call theuser can then talk and listen through handset 804. If the call is notanswered by the user after a selectable time delay, or mobile end system102 determines that it cannot accept the call at this time, for exampleif higher layer data communication protocols have priority forcommunications, a disconnect signalling message is sent to mobile dataswitch 208 in block 913 and packet data communication is resumed.

Variations

Design variations are possible within the system structure outlinedabove. Some possible variations are outlined below.

A fixed telephone 124 has been shown throughout, however many otherdevices can reasonably be substituted, including facsimile devices,voice mail, pagers, or switched circuit modems.

An alternate method may be used to set up switched circuit calls to acellular switch system 105. In this method a roamer directory number isprovided by cellular switch system 105 for roaming cellular mobile endsystems. Call establishment proceeds by initiating a call to the roamerdirectory number, and cellular switch system 105 then applies dial tone.Once circuit switch 407 detects this dial tone, the cellular mobileidentification number is sent from circuit switch 407 using DTMF inbandsignalling. This procedure is an alternative to sending a route requestmessage and originating a call to the returned temporary directorynumber.

Additional routing information may be communicated from the mobile endsystem 102 to mobile routing register 203 as packet data, for example analternate directory number for routing voice calls may be provided, orthe bearer services available at mobile end system 102 can berestricted.

Determination by mobile end system 102 of its current location, whentelephone access gateway 104 is selected as the preferred subnetworkconnection device, may involve manual entry by the user of mobile endsystem 102, or the directory number may be determined by originating acall to circuit switch 407. Telephone caller identification features canthen be used by mobile circuit control 402 to determine the originatingnumber, which is the directory number for the point of connection oftelephone access gateway 104. Mobile circuit control 402 can thenforward the current location to mobile routing register 203 aspreviously described.

The design described above represents mobile routing network 101 asincorporating the CDPD mobile serving function, and cellular packet datasystem 106 as incorporating the CDPD mobile home function, where themobile home function is the destination point for static packet routingin packet data network 108. A variation on this design would allowcellular packet data system 106 to incorporate the CDPD mobile servingfunction and incorporate the CDPD mobile home function in mobile routingnetwork 101. In this variant, static routing tables in packet datanetwork 108 would deliver packets to mobile routing network 101, wherethey would be routed according to the location information provided bycellular packet data system 106.

While the invention has been particularly shown as described withrespect to a preferred embodiment thereof, it will be understood bythose skilled in the art that changes in form and details may be madetherein without departing from the scope and spirit of the invention.

I claim:
 1. An apparatus for connecting a mobile end system to acommunications network comprising:a mobile end system incorporatingstorage means and having assigned thereto a first unique identity code;an interface device including a first transmission means and havingassigned thereto a second unique identity code, said interface devicebeing linked to said mobile end system via a first communicationschannel; and data switch means including a second transmission means andhaving assigned thereto a third unique identity code, said data switchmeans being linked to said interface device via a second communicationschannel and being additionally linked to a communications network via athird communications channel; wherein said mobile end systemcommunicates with said interface device by transmitting at least saidfirst unique identity code thereto and wherein said interface devicecommunicates with said data switch by transmitting at least said firstand second unique identity codes thereto and said data switch meanscommunicates said third unique identity code as well as said first andsecond unique identity codes to said communications network.
 2. Theapparatus according to claim 1, wherein said communications networkfurther comprises a telephone switch connectable to said mobile endsystem via said interface device.
 3. The apparatus according to claim 2,wherein said second unique identity code of said interface devicecomprises a telephone number, and said first transmission meanscomprises the establishment of a telephone call from said interfacedevice to a third transmission means attached to said telephone switch.4. The apparatus according to claim 3, wherein said telephone switchtransmits said second unique identity code to said third transmissionmeans, which in turn transmits said telephone number to said data switchmeans.
 5. The apparatus according to claim 4, wherein saidcommunications network further comprises a packet data network linked tosaid mobile end system through said interface device, and wherein saidpacket data network is assigned a unique identity means which comprisesan address within said packet data network.
 6. The apparatus accordingto claim 5 wherein said interface device includes an associated storagemeans for storing said second unique identity code.
 7. The apparatusaccording to claim 1 wherein the communications network is either afixed end system or a mobile end system.
 8. The apparatus according toclaim 1 wherein the location of the mobile end system is stored within amobile routing register.
 9. The apparatus according to claim 8 whereinsaid location comprises information to identify connection means forpacket data communication.
 10. The apparatus according to claim 9wherein said connection means comprises means for routing the datapackets.
 11. The apparatus according to claim 1, wherein said dataswitch means and said mobile end system comprise a modem and whereinsaid switching transmission means comprise setting up a switched circuitfrom said data switch to said interface device, for transmission of thedata packets from said data switching modem to said mobile end systemmodem.
 12. The apparatus according to claim 1, wherein saidcommunications network comprises a cellular packet data network, acellular telephone switch and telephone circuits.
 13. The apparatusaccording to claim 1 wherein a cellular intersystem roaming protocol isused for identification of routing to be used for packet routing whereina cellular telephone is to transmit a predetermined uniqueidentification code to a cellular telephone switch which is to transmitsaid identification code to said data switch.
 14. The apparatusaccording to claim 13, wherein a cellular telephone switch, whichcomprises connection means for connecting radio channels to saidtelephone circuits, and said mobile end system communicate by means ofswitched circuit radio channel, and wherein said data packet comprisescommands to said mobile end system to switch to said switched circuitradio channel.
 15. The apparatus according to claim 14, whereininterface means comprises a cellular packet data radio or a packet radiochannel, which transmits a predetermined unique identification code tosaid cellular packet data system which in turn transmits saididentification code to the data switch.
 16. The apparatus according toclaim 1, wherein said communications network comprises a circuit switchconnected to a switched telephone network, linking it to said dataswitch, via one or more telephone circuits, which comprise signallingmeans for establishing switched circuits.
 17. The apparatus according toclaim 16, wherein said circuit switch sends data packets to said dataswitch for establishing a switched circuit between said interfacedevice, comprising said switched circuit communication means and saidcircuit switch.
 18. The apparatus according to claim 16, wherein saidcircuit switch forwards incoming calls to a directory number accordingto the identity of said interface device.
 19. A method of communicatingdata packets bidirectionally between a mobile end system and either afixed end system or a second mobile end system, said mobile end systembeing coupled to one or more subnetwork communication devices tocommunicate with a circuit switched network or packet data network, saidmethod comprising the steps of:assigning unique identity codes at leastone mobile end system, an interface device and a data switch means;setting up communication channels between an originating device and aterminating device, one of which is said mobile end system; identifyinga routing scheme to be used for packet transmission; and establishingbidirectional communications between said originating device and saidterminating device.
 20. The method according to claim 19, wherein saidbidirectional communications between said originating device and saidterminating device is via either a packet data network or a circuitswitched network.
 21. The method according to claim 19, wherein saidmobile end system is coupled to one or more subnetwork communicationdevices, and said mobile end system determines its location andavailable connection means by monitoring said subnetwork connectiondevices.
 22. The method according to claim 19, wherein a mobile routingregister sends a route flush request.
 23. The method according to claim19, wherein call setup packets are interpreted by a mobile end systemcontrol in order to establish a path through an audio path switch to amodem and packet processor.